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Re: [Qemu-devel] [PATCH] coroutine: Fix documentation of co_aio_sleep_ns

From: Eric Blake
Subject: Re: [Qemu-devel] [PATCH] coroutine: Fix documentation of co_aio_sleep_ns()
Date: Wed, 8 Nov 2017 11:42:01 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0

On 11/08/2017 11:36 AM, Stefan Hajnoczi wrote:

>> This function uses timers and hence needs to know the event loop
>> (#AioContext) to place the timer on.  After the time elapses, the
>> current coroutine will restart with the same #AioContext it is currently
>> running in, even if that is different than the timer context passed to
>> co_aio_sleep_ns().
> These complicated semantics are a clue that the API should be
> simplified.  QEMU has changed since this function was first introduced.
> Now we can do the following:
>   void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns)
>   {
>       AioContext *ctx = qemu_get_current_aio_context();
>       CoSleepCB sleep_cb = {
>           .co = qemu_coroutine_self(),
>       };
>       sleep_cb.ts = aio_timer_new(ctx, type, SCALE_NS, co_sleep_cb, 
> &sleep_cb);
>       timer_mod(sleep_cb.ts, qemu_clock_get_ns(type) + ns);
>       qemu_coroutine_yield();
>       timer_del(sleep_cb.ts);
>       timer_free(sleep_cb.ts);
>   }
> I don't see a reason for the caller to pass in an AioContext.
> Any objections?  Will send a patch if this is okay.

Makes sense to me.

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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